CBSE Class 12 Physics 2022 Term 2 Delhi Set 1 Solved Paper

Question : 9

Total: 12

(a) Calculate the energy and momentum of a photon in a monochromatic beam of wavelength 331.5nm.3
(b) How fast should a hydrogen atom travel in order to have the same momentum as that of the photon in part (a)?

Solution:

(a) Energy =E=

Or, E=

6.6×10−34×3×108

331.5×10−9

∴E=6×10−19J
Momentum =p=

Or, p=

6.6×10−34

331.5×10−9

∴p=2×10−27kg.m∕s
(b) Momentum of Hydrogen atom
=p=2×10−27kg.m∕s
p=mv
Or, v=

Or, v=

2×1027kg.m∕s

1a.m.u.

Or, v=

2×10−27kg.m∕s

1.66×10−27kg

∴v=1.2m∕s

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